Various microorganisms are known to have a beneficial effect on plants. These microorganisms include bacteria of the genera Rhizobium, Bradyrhizobium, Sinorhizobium, Mesorhizobium, Pseudomonas, Serratia, Bacillus, Paenibacillus, Pasteuria, Azotobacter, Enterobacter, Azospirillum, Methylobacterium, Cyanobacteria (blue-green algae), and mycorrhizal fungae. Such microorganisms can be introduced to the plants by the use of inoculant compositions. The process by which inoculant compositions are created includes the step of fermenting the microorganisms, generally on a nutrient media.
The inoculant compositions can be applied directly onto seeds of plants or can be applied in furrow immediately prior to the seeds being planted. Inoculation of the seeds or soil with beneficial microorganisms for crop improvement has been practiced for a number of years. However, variable and inconsistent results have often been observed, possibly due to loss of inoculant viability or variability of dosage due to changes in inoculant viability.
When an inoculant is applied at the time of sowing, whether in furrow application or by on-seed application, the microorganisms in the inoculant do not have time to adjust to the new environment. Consequently, the microorganisms in the inoculant may have a low rate of survival.
Currently, to improve viability of the microorganisms in the inoculant, extenders based on sugars or polymers are added when the inoculant is added to the seed, or at the time of sowing. Because the extenders are added after packaging of the inoculant, the extenders have no effect on the survival and stability of the inoculant in pack.
Also, the addition of extenders at the time the inoculant is added to the seed or at the time of sowing is cumbersome and generally must be performed by the end-users of the inoculant (e.g., farmers) in a non-controlled environment (e.g., in a barn or in a farm field). Thus, there is an increased likelihood that the extenders will be improperly applied.
To overcome the problems associated with adding extenders after the inoculant is prepared, extenders have also been added to the nutrient medium prior to the fermentation step of creating the liquid inoculant. However, addition of the extenders, at an optimal level for on-seed survival, before fermentation inhibits growth of the microorganisms.
Therefore, there is a need for a method for increasing survival and stability of a microorganism (e.g., bacteria) of a liquid inoculant during storage, and for improving on-seed survival and stability of a microorganism of a liquid inoculant once placed on a seed.